Discovery and in Vivo Evaluation of Macrocyclic Mcl-1 Inhibitors Featuring an α-Hydroxy Phenylacetic Acid Pharmacophore or Bioisostere.

Overexpression of the antiapoptotic protein Mcl-1 provides a survival advantage to some cancer cells, making inhibition of this protein an attractive therapeutic target for the treatment of certain types of tumors. Herein, we report our efforts toward the identification of a novel series of macrocyclic Mcl-1 inhibitors featuring an α-hydroxy phenylacetic acid pharmacophore or bioisostere. This work led to the discovery of 1, a potent Mcl-1 inhibitor (IC50 = 19 nM in an OPM-2 cell viability assay) with good pharmacokinetic properties and excellent in vivo efficacy in an OPM-2 multiple myeloma xenograft model.

AMG 176, a Selective MCL1 Inhibitor, Is Effective in Hematologic Cancer Models Alone and in Combination with Established Therapies.

The prosurvival BCL2 family member MCL1 is frequently dysregulated in cancer. To overcome the significant challenges associated with inhibition of MCL1 protein-protein interactions, we rigorously applied small-molecule conformational restriction, which culminated in the discovery of AMG 176, the first selective MCL1 inhibitor to be studied in humans. We demonstrate that MCL1 inhibition induces a rapid and committed step toward apoptosis in subsets of hematologic cancer cell lines, tumor xenograft models, and primary patient samples. With the use of a human MCL1 knock-in mouse, we demonstrate that MCL1 inhibition at active doses of AMG 176 is tolerated and correlates with clear pharmacodynamic effects, demonstrated by reductions in B cells, monocytes, and neutrophils. Furthermore, the combination of AMG 176 and venetoclax is synergistic in acute myeloid leukemia (AML) tumor models and in primary patient samples at tolerated doses. These results highlight the therapeutic promise of AMG 176 and the potential for combinations with other BH3 mimetics. SIGNIFICANCE: AMG 176 is a potent, selective, and orally bioavailable MCL1 inhibitor that induces a rapid commitment to apoptosis in models of hematologic malignancies. The synergistic combination of AMG 176 and venetoclax demonstrates robust activity in models of AML at tolerated doses, highlighting the promise of BH3-mimetic combinations in hematologic cancers.See related commentary by Leber et al., p. 1511.This article is highlighted in the In This Issue feature, p. 1494.

Biosynthesis, asymmetric synthesis, and pharmacology, including cellular targets, of the pyrrole-2-aminoimidazole marine alkaloids.

The pyrrole-2-aminoimidazole (P-2-AI) alkaloids are a growing family of marine alkaloids, now numbering well over 150 members, with high topographical and biological information content. Their intriguing structural complexity, rich and compact stereochemical content, high N to C ratio (~1 : 2), and increasingly studied biological activities are attracting a growing number of researchers from numerous disciplines world-wide. This review surveys advances in this area with a focus on the structural diversity, biosynthetic hypotheses with increasing, but still rare, verifying experimental studies, asymmetric syntheses, and biological studies, including cellular target receptor isolation studies, of this stimulating and exciting alkaloid family.

Synthesis of novel beta-lactone inhibitors of fatty acid synthase.

Fatty acid synthase (FAS) is necessary for growth and survival of tumor cells and is a promising drug target for oncology. Here, we report on the syntheses and activity of novel inhibitors of the thioesterase domain of FAS. Using the structure of orlistat as a starting point, which contains a beta-lactone as the central pharmacophore, 28 novel congeners were synthesized and examined. Structural features such as the length of the alpha- and beta-alkyl chains, their chemical composition, and amino ester substitutions were altered and the resulting compounds explored for inhibitory activity toward the thioesterase domain of FAS. Nineteen congeners show improved potency for FAS in biochemical assays relative to orlistat. Three of that subset, including the natural product valilactone, also display an increased potency in inducing tumor cell death and improved solubility compared to orlistat. These findings support the idea that an orlistat congener can be optimized for use in a preclinical drug design and for clinical drug development.

Facile synthesis of the trans-fused azabicyclo[3.3.0]octane core of the palau'amines and the tricyclic core of the axinellamines from a common intermediate.

A facile synthesis of the trans-fused azabicyclo[3.3.0]octane core of palau'amine and related pyrrole-imidazole alkaloids is described. Following gamma-lactam cleavage with concomitant epimerization at C12 of a previously reported tricycle, a facile intramolecular Mitsunobu reaction delivered the fully functionalized tricyclic core common to several members of the oroidin-derived alkaloids including palau'amine. An alternative cyclization of a related intermediate provides the tricyclic "aza-angular triquinane" core of the axinellamines.

Total synthesis and comparative analysis of orlistat, valilactone, and a transposed orlistat derivative: Inhibitors of fatty acid synthase.

Concise syntheses of orlistat (Xenical), a two-carbon transposed orlistat derivative, and valilactone are described that employ the tandem Mukaiyama aldol-lactonization (TMAL) process as a key step. This process allows facile modification of the alpha-side chain. Versatile strategies for modifying the delta-side chain are described, involving cuprate addition and olefin metathesis. Comparative antagonistic activity of these derivatives toward a recombinant form of the thioesterase domain of fatty acid synthase is reported along with comparative activity-based profiling.